Heat and chemical resistant metal alloy parts



United States Patent 3,337,427 HEAT AND CHEMICAL RESISTANT METAL ALLOY PARTS Marshall G. Whitfield, Brookfield, and Richard S. Parzuchowski, Danbury, Conn. (both Whitfield Laboratories, Inc., P.0. Box 293, Bethe], Conn. 06801) No Drawing. Filed June 27, 1966, Ser. No. 560,886 2 Claims. (Cl. 204-37) ABSTRACT OF THE DISCLOSURE A heat-resistant metal alloy article and method of manufacturing the same, wherein a base metal portion containing nickel, cobalt or iron is given an outer metallic alloy layer containing chromium, beryllium and aluminum to enable it to resist sulphidation to a greater degree.

This invention relates to metal parts which are especially resistant to elevated temperatures and chemical attack, and to methods of producing the same.

Metal parts of the above nature are useful in gas turbines, as blade components, combustion liners, fuel-air nozzles and the like where it is important to have protection against melting, oxidation, sulphidation, corrosion and erosion, mechanical failure, fatigue, etc.

With such parts the adverse effects of sulphidation due to salt air and corrosive agents are especially harmful.

The invention is especially concerned with metal parts and methods of producing the same, wherein surface and subsurface alloys act in conjunction with the base material, to effect the desired result. The invention is applicable to base materials which have a preponderance of nickel, or of cobalt, or of iron in their make-up.

Objects of the invention are to provide improved methods and articles produced thereby, by which greater heat and chemical resistance may be obtained in metallic parts intended for use in gas turbines and other high temperature equipment; to provide improved methods and articles involving the alloying of nickel, cobalt or iron type base materials with beryllium and aluminum to produce the desired improved procedures and characteristics; to provide an improved pack cementation mix and heat alloying procedure, and improved metal parts involving the above materials, and involving as well the additional alloying metals of silicon, chromium, nickel and tantalum, wherein unexpectedly increased resistance is had to sulphidation, erosion, corrosion and oxidation.

As engine technology advances and engine operating temperatures are increased, the problem of sulphidation of heated engine parts becomes more acute, the effects of this type of action being increasingly severe with each advance in engine performance.

Sulphidation becomes severe in an environment having salt air, as for example over sea water. The sodium chloride in such environment can result in.reactions in the presence of the burning fuel, as for example the following: Na SO +9/2NiNa O-l-3NiO+%Ni S The sodium comes from the salt in the air, and the 80,, comes from the fuel being burned. The result is an especially adverse effect on heated metal surfaces which would otherwise successfully resist oxidation, corrosion and erosion.

A particularly important object of the invention is, therefore, to provide rugged alloyed metal parts which are especially resistant to the effects of sulphidation.

Other features and advantages will hereinafter appear.

The present invention attains the above objectives by incorporating in the surface alloys of the metal parts, the metal beryllium in addition to aluminum and chromium, and in some circumstances with the inclusion of nickel and/or tantalum.

Examples of procedures by which the invention is carried out, are as follows:

EXAMPLE 1 and given a diffusion heat treatment for /2 hour at 2000 F. A coating of approximately five mils of alloy is found on parts treated in this manner.

EXAMPLE 2 Electrolytic deposition is employed, to deposit one mil of nickel on the metal parts to be treated. This is followed by a diffusion heat treatment of /2 hour at 1900" F. The parts are then coated according to the procedure outlined in Example 1, with a resultant coating of approximately six mils being effected.

EXAMPLE 3 A cementation mix is prepared, composed of commercial grade aluminum oxide particles having a size of 220 mesh, having 5% beryllium powder grade GB-2 and size 325 mesh, and 5% aluminum powder of size -325 mesh, to which is added 35 grams of ammonium fluoride per pounds of mix. The ammonium fluoride acts as the active gas-producing ingredient. The mix is packed about the metal parts to be treated, and is heated to 19l0 F.+10 for three hours and thereafter allowed to cool. The metal parts are removed, washed and given a diffusion heat treatment for A2 hour at 2000 F. A coating of approximately five mils of alloy is found on parts treated as above.

, EXAMPLE 4 Electrolytic deposition is employed, to deposit one mil of nickel on the metal parts which are to be treated, This is followed by a diffusion heat treatment for /2 hour at 1900" F. The metal parts are then coated according to the procedure outlined in Example 3, With a resultant coating of approximately six mils being obtained.

EXAMPLE 5 A bath of aluminum-beryllium alloy containing 5% to 10% beryllium is prepared, and heated to 1800 F. This is used to coat engine blades or vanes as 'by dipping the prepared pieces in the bath. After coating of the pieces, the excess molten metal is removed by brushing, vibrating or otherwise. The initial coating is then diffused to form the final alloy coating, by heating the pieces in a neutral or reducing atmosphere for approximately /2 hour at 2000 F. to give a final overall alloy thickness of 4 mils. The diffusion will vary with the base alloy heat treatment and with the temperature to which the parts are subjected.

EXAMPLE 6 A cementation mix is prepared, consisting of 1.5% beryllium powder having a size of l.00 mesh, and consisting of 98.5% aluminum oxide having a sizeof 220 mesh, to which is added 35 grams of ammonium fluoride per 100 pounds of mix. The ammonium fluoride acts as the gas-producing ingredient. The mix is packed about the metal parts which are to be treated, and the pack is then heated to 1550i10 F. for two hours, after which it is allowed to cool. The metal parts are removed,

Washed and given a diifusion heat treatment for /2 hour at 2000 F. A coating of approximately five mils of alloy is formed on the metal parts as above treated.

EXAMPLE 7 Electrolytic deposition is utilized to effect deposition of one mil of nickel on the metal parts. This is followed by a diffusion heat treatment for /2 hour at 1900 F. The parts are then coated according to the procedure outlined in Example 6, to obtain a resultant coating of approximately six mils.

EXAMPLE 8 The metal parts to be treated are provided with a coating of tantalum, to a thickness of from one-half to one mil approximately. Thereafter the parts are given a pack cementation treatment according to any of the foregoing examples.

Typical compositions of metal parts suitable for use with the above examples are as follows:

Nickel B ase Composition obalt B ase Composition Iron Base Composition *Maximum.

Metal parts treated according to the above Example 6 using a nickel base material known commercially as 713C, tested as follows:

On erosion test for 100 hours 2100 F., a weight change of +0105 gram was observed. On sulphidation test for 40 hours at 1800 F, a weight change of 0.066 gram was observed.

vWith a plain aluminum coating, a sample placed on erosion test showed a weight change of 0.088 gram. With an aluminum-chrome coating, the weight change was 0.031 gram, and on sulphidation test for 40 hours at 1800 F. a weight change of 0.632 gram was observed.

Considering an erosion test with an aluminum-chromesilicon coating, the weight change was -0.035 gram. On

4 sulphidation test for 40 hours at 1800 F. a weight change of 0.l11 gram was observed.

Considering an erosion test with an uncoated sample, there was a weight change of 0.307 gram. On sulphidation test for 40 hours at 1800 F. a weight change of 4.36() grams.

From the foregoing test results it is clearly seen that the presence of beryllium in the surface alloy of the treated pieces has resulted in a decided improvement in erosion-resisting properties, including resistance to sulphidation, whereby there is had a more rugged and durable product capable of extended life under adverse conditions such as encountered in gas turbines and the like.

It has been determined that moderate amounts of chromium have not adversely affected the resistance to erosion. Also, the presence of the tantalum has been found to be of benefit. As understood at present the tantalum alloys with the beryllium and this further increases the resistance to erosion and sulphidation.

We claim:

1. The method of manufacturing a metal article made of a heat-resistant alloy containing as the main constituent at least one of the metals nickel, cobalt and iron and also containing chromium, which includes the steps of electroplating the article with nickel, heating the article for approximately one-half hour at approximately 1900 F. to diffuse the nickel into the article, packing the article in a mixture containing beryllium and a halide, and heating the article and pack for approximately eight hours at approximately 1900 F. to alloy surface portions of the article with beryllium, cooling, removing and Washing the article, and thereafter heating the article for approximately one-half hour at approximately 2000 F. to further diffuse the alloyed beryllium into the article.

2. The method of manufacturing a metal article made of a heat-resistant alloy containing as the main constituent at least one of the metals nickel, cobalt and iron and also containing chromium, which includes the steps of coating the article with tantalum, packing the article in a mixture containing beryllium and a halide, and heating the article and pack for approximately eight hours at approximately 1900 F. to alloy surface portions of the article with beryllium, cooling, removing and washing the article, and thereafter heating the article for approximately one-half hour at approximately 2000 F. to further diffuse the alloyed beryllium into the article.

References Cited HYLAND BIZOT, Primary Examiner. 

1. THE METHOD OF MANUFACTURING A METAL ARTICLE MADE OF A HEAT-RESISANT ALLOY CONTAINING AS THE MAIN CONSTITUENT AT LEAST ONE OF THE METALS NICKEL, COBALT AND IRON AND ALSO CONTAINING CHROMIUM, WHICH INCLUDES THE STEPS OF ELECTROPLATING THE ARTICLE WITH NICKEL, HEATING THE ARTICLE FOR APPROXIMATELY ONE-HALF HOUR AT APPROXIMATELY 1900* F. TO DIFFUSE THE NICKEL INTO THE ARTICLE, PACKING THE ARTICLE IN A MIXTURE CONTAINING BERYLLIUM AND A HALIDE, AND HEATING THE ARTICLE AND PACK FOR APPROXIMATELY EIGHT HOURS AT APPROXIMATELY 1900*F. TO ALLOY SURFACE PORTIONS OF THE ARTICLE WITH BERYLLIUM, COOLING, REMOVING AND WASHING THE ARTICLE, AND THEREAFTER HEATING THE ARTICLE FOR APPROXIMATELY ONE-HALF HOUR AT APPROXIMATELY 2000*F. TO FURTHER DIFFUSE THE ALLOYED BERYLLIUM INTO THE ARTICLE. 